Gunnar Ottosson’s linseed oil paint glossary

If you have any questions, please contact us by telephone or e-mail: +46 40 48 25 74 or info@ottossonfarg.com

Application

Linseed oil paint should al- ways be applied thinly. The paint does not spread out by itself but must be well distributed using a paintbrush. The paint must be applied in even coats. If the paint is applied on the surface in varying thicknesses it will be noticed by devel- oping an uneven gloss. Using a varnish roller, the paint can also be rolled thinly onto an even surface [e.g. sheet mate- rial, metal, smooth plaster]. In general, linseed oil paint can be applied using a variety of methods and tools provided it is done in thin, even coatings.

Working temperature

The paint con- tains no water and can withstand frost. Application of the first coat can be carried out during minus tem- peratures provided the substrate is dry and the paint is kept at room temper- ature. The optimal temperature for painting is 15 – 25o C.

Fire risk

Rags soaked in linseed oil can combust spontaneously. Soak the rag in water after use and dispose of it in a container with a lid.

Economy

If you estimate the price per square metre rather than the price per litre you will be surprised as to how cheap linseed oil paint actually is. Lin- seed oil paint covers 2-3 times the sur- face area per litre compared to other types of paint.

Gloss

After three coats the paint has a high gloss finish which will gradually become more matt until after approx. 3-4 months when it will have acquired its final semi gloss finish [gloss scale 30-40]. Often when painting indoors, the high gloss finish is noticed immedi- ately after applying the final coat but already after a week a more matt finish will be seen.

Yellowing

Linseed oil yellows in the dark and fades in the light. This means no yellowing takes place outdoors, insig- nificant yellowing takes place indoors in rooms with daylight and intense yel- lowing in rooms without daylight. This yellowing process is reversible i.e. a surface that has yellowed in the dark and which is then exposed to light will revert to its original shade and the yel- lowing will disappear.

Streaks

can occur when the linseed oil penetrates unevenly into the substrate and the shade of the paint appears darker. Uneven penetration can result in blotchy bright | dull, light | dark surfac- es. Particularly when painting indoors where greater demand is required to achieve an even finish, this blotchiness can cause a degree of concern when ap- plying the primer and middle coats. This is most clearly seen when applying grey shades. Before applying the final coat, areas that absorb a lot must first be pre- pared in order to create an evenly absor- bent substrate. Follow the drying times and apply the paint evenly. Stains can also occur as a result of excessive dew formation. Avoid painting during damp autumn evenings.

Storage

of linseed oil paint can take place indefinitely provided no oxygen comes in contact with the paint. When storing paint in an already opened con- tainer, cover the surface of the paint with a plastic bag and replace the lid securely so that no air can enter. The paint is best stored in a cool place and it can withstand frost. During long storage periods the colour pigments can sink to the bottom. Therefore, make sure the paint is stirred well be- fore reuse.

Solvents / dilution

Apart from some exceptions [see the colour samples], the paint contains no solvents. In cases where dilution using solvents is indi- cated, we refer to Balsam turpentine [oleo-resin balsam], which consists of 100% vegetable turpentine, distilled from conifer resin. Turpentine has the ability of transporting oxygen which improves the drying process. The user who has diluted the paint with min- eral solvents such as white spirit and aliphatic naphtha has also had good results. When painting indoors it is im- portant to follow the safety directions concerning the respective solvent. Sol- vents are a technical aid facilitating the work of painting. Many of our cus- tomers use our paints to good effect without diluting them with solvents. See our directions for use.

Mould / algae attack

on the painted surface is unusual but may occur out- doors. Most often it appears as small black dots [of earthy character]. These are located on the surface and, other than for aesthetical reasons, do not affect the function of the paint. If the attack is intensive and troublesome, wash it off using algae | mould soap. Washing-up detergent also functions well. The reason for the attack can be due to the wood already being affect- ed. Mould attack from the surrounding environment is difficult to trace. Old dry grass is known to be a cause. The attack takes place very differently lo- cally and the extent can change from year to year. No fungicide additives are used in our paints. However, zinc oxide, which we consider has a more long-term effect, is included in all our linseed oil paints.

Oxidation & drying

takes place when lin- seed oil comes in contact with oxygen in the air. Light and heat accelerate the process. Generally, linseed oil paint dries between 1-5 days depending on external conditions. Drying takes place best outdoors during the summer months. When painting indoors during the winter months, we recommend the addition of 10 ml extra drying agent per 1 litre of paint. In an unheated dark cellar, the paint dries very slowly. The cold delays the oxidation process.

Pigments

Traditionally inorganic pig- ments have always been used with lin- seed oil paints. Such pigments include e.g. all earth pigments, iron oxides and other metal compounds. In recent years, environmental legislation has forbidden the use of cadmium, chromium and lead in building materials. Previously they were used commonly when producing strong colour shades. Modern research has developed new environmentally friendly inorganic pigments, which we now use.

Cleaning

of hands and paintbrushes is best done using soap and water. Sol- vents can also be used. Do NOT use soap on painted surfaces!

Furrow forming

on surfaces after painting is an indication that the paint has been applied too thickly. Furrows often occur in profiles where too much paint can easily collect. If the paint is cold it thickens and the risk of painting too thickly subsequently increases.

Shellac

is a spirit-soluble secretion ob- tained from an Asiatic scale insect. In painting terminology [often referred to as knotting varnish], it is used to insu- late knots and resin flakes on wood in- doors prior to painting. If shellac is not used, the resin can penetrate or bleed through the painted surface and result in a discolouration in the form of brown stains. Shellac varnish is applied primar- ily on pine surfaces. Spruce is considered less susceptible to risk from resin bleed- ing. Shellac is applied relatively plenti- fully 1-2 times and can be painted over after half an hour. Should the resin con- tinue to penetrate after painting, shellac can be re-applied on the painted surface afterwards. Shellac can also be used on strongly absorbent fillers to reduce ab- sorption in the substrate.

Substrates

which may consist of various types of wood, plaster, gypsum or metal must be dry with a moisture content below 15% and have a neutral pH value. Paint- ing directly on paper or textiles is not recommended as the oxidation process of linseed oil can make the material brittle. Insolate the underlying surface first using an adhesive substance or emulsion paint. Silicon based and waxed surfaces cannot be painted over.

Adhesion

Linseed oil has fantastic adhesion properties and in general ad- heres to all types of surfaces. In our experience the paint adheres well even when applied to surfaces painted with other types of paint.